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Wednesday, October 21, 2015

Thrombus Load May Predict Worse Outcome after EVAR

New research in the current issue of JVIR evaluated the impact of two- and three-dimensional preoperative morphologic assessment on CTA on midterm outcomes in patients with AAA treated with EVAR. Sirignano et al., retrospectively evaluated morphologic features of AAA including maximum aortic diameter, thrombus area, overall aneurysm volume, and intrasac thrombus volume (1). This was compared with all perioperative and midterm AAA-related re-intervention and all-cause mortality. Investigators reviewed 191 pre-op CTAs with mean maximum aortic diameter of 58 mm; thrombus area, 49.6%; aortic volume, 159.36 cm3; and thrombus volume, 58.6%. There were no reported cases of re-intervention or mortality in the perioperative period. Mean follow-up was 32 months +/- 16.8 months (range, 3-66 months) with a mortality rate of 9.4%. AAA-related death was 0 and re-intervention rate was a low 8.9%. Causes of re-intervention included type I endoleak (n=3 [1.6%]), type II endoleak (n=7 [3.7%]), type III endoleak (n=1 [0.5%]), endograft limb thrombosis (n=4 [2.1%]), and access vessel thrombosis (n=2; 1%). Predictors for re-intervention included greater thrombus area (>60%) and thrombus volume (>59%). While greater maximum aortic diameter (>59 mm) and aortic volume (>159 cm3) trended to higher reintervention rate, the results were not statistically significant (P=.62 and P =.12). Aortic volume was a predictor of any adverse event, re-intervention, and all-cause mortality after EVAR (P=.03). The authors concluded that thrombus area and volume are risk factors for higher rates of re-intervention and do not represent a protective factor.

Commentary:

The above article is noteworthy as it challenges a commonly held assumption regarding sac thrombus and re-intervention rates. While previous work (2, 3) has suggested that thrombus load is actually protective of future interventions (namely type II endoleak), the current manuscript has shown that this assumption may not be valid. However, the current study has a smaller sample size and a lower rate of re-intervention (8.9% vs 15.4%) when compared with prior work. Further, earlier research focused more on presence or absence of endoleak rather than growth or shrinkage of sac size. Additionally, given changes in device design, one may argue how comparable two sample cohorts from >10yrs apart are. Lastly, given the large number of variables present (neck angulation, neck length, presence or absence of patent vessels within the sac, etc.) it may be difficult to tease out meaningful conclusions from a small data set. Regardless, if nothing else, the questions raised in the manuscript point to the continued need for research in this challenging patient population.